According to the prior art, a non-inflammable agent is an important additive to a polymer and is intended to modify the combustibility of inflammable materials and thereby enhance the capability of the polymer to be non-inflammable, spontaneously stop burning, and not emit smoke, thereby preventing the polymer from staying active and spreading. Conventional halogen-containing non-inflammable agents in wide use display high efficiency of flame retardation, incur low manufacturing costs, and are highly compatible with the other related materials. But, when burning, conventional halogen-containing non-inflammable agents in wide use undergo decomposition to thereby produce highly toxic, corrosive gases and emit thick smoke to the detriment of public health and environmental protection. With environmental awareness on the rise, green legislations are enacted by governments to ban halogen-containing non-inflammable agent, thereby justifying the urgency and necessity of development of halogen-free non-inflammable agents.
Halogen-free silicon-containing non-inflammable agents are advantageously non-toxic and emit little smoke, but inorganic silicon-containing non-inflammable agents sometimes exhibit incompatibilities with polymer substrates and therefore cause the detriment of the physical properties and processibility of polymer substrates. As a result, polymer substrates must contain the other additive or filler in order to effectuate optimal flame retardation. By contrast, organic silicone-containing non-inflammable agents are non-toxic, prevent melt drops and emit little smoke during combustion, display high flame retardation efficiency, are environmentally friendly for being halogen-free, and thus have a more promising future applicability.
Depending on their constituent groups, silicone non-inflammable agents fall into two categories: organosiloxane and silicone rubber. The two categories differ slightly in the main chain structure. The main chain of organosiloxane consists of repeating —R2Si—O— bonds, wherein silicon atoms are substituted with saturated alkyl, vinyl, phenyl or the other organic groups. Furthermore, organosiloxane often mixes with an additive or filler, such as aluminum hydroxide to enhance its non-inflammable property, albeit at the cost of material compatibility and processibility, not to mention ending up with the following disadvantages: releasing water from its hydrated complex at high temperature, generating bubbles inside the polymeric material to the detriment of appearance, and deteriorating the capability of the material to be waterproof and electrically insulating.
Like organosiloxane, the main chain of silicone rubber consists of repeating Si—O—Si bonds, wherein silicon atoms are attached with saturated alkyl, vinyl, phenyl or the other organic groups. By contrast, the main chain of silicone rubber usually builds with rigid organic aryl groups, such as phenylene, to increase the insulating charring layer content generated during combustion, and in consequence a dense and stable silicon-containing charring protective layer will be formed firmly on the surface of the substrate in order to block external heat and oxygen, so as to prevent the polymer material from undergoing thermal degradation or producing inflammable volatile substances, and prevent melt drops during combustion.
Both silicone rubber and its elastomer are non-toxic, prevent melt drops upon combustion, emit little smoke, display high flame retardation efficiency, and are thermally stable, electrically insulating, resistant to chemicals, waterproof, and oil-proof. Therefore they are applicable to various industrial hermetic seal materials, non-inflammable materials, heat resistant materials, plastic materials, coating materials, packing materials, adhering glues, electrically insulated products, medical equipment for heat-resistant sterilization, and artificial films.
MacKnight and others performed polycondensation with recrystallized para-phenylene disilanol and high-purity diamino silane to produce a polymer with alternating para-phenylene silicon and siloxane structure. The polymer thus produced is tested by thermal analysis, and the molecular weight of the polymer is analyzed by gel permeation chromatography (GPC); the results show that the process method produces a thermally-satisfactory non-inflammable polymer from a silicone rubber elastomer. However, the polymer produced by the method incurs high processing costs, and the technique of separation and purification is not suitable for mass production. Furthermore, the polymer with alternating para-phenylene silicon and siloxane structure mostly exists in the form of a highly viscous liquid gel or an elastomer, as with the filtration and collection techniques of the method disclosed in the prior art, showing that the conventional method fails to separate and purify the polymer efficiently and in a high yield.
The monomer compounds, such as para-phenylene disilanol and dimethylaminosilane, required for producing the polymer are pricey. The production of the polymer necessitates intricate processing and reaction steps. As a result, the production of the polymer is not suitable for mass production. Furthermore, MacKnight and others disclosed that, when purchased commercially, the compound which consists of para-phenylene disilanol monomer requires undergoing additional recrystallization and purification processes which involve using internationally banned and toxic carbon tetrachloride as a recrystallizing solvent to the detriment of industrial development and environmental sustainability. Another solvent which has ever been used in recrystallization and purification processes is toluene which dissolves para-phenylene disilanol monomer compounds to a certain extent, thus fails to meet the requirements for the purification process and recycling rate of the monomer compounds. To avoid using expensive commercially available monomer sources, the prior art discloses that synthesis process of para-phenylene disilanol monomer compounds entails performing alkoxide substitution reaction with para-phenylene disilane precursor and then performing hydrolysis, so as to produce the para-phenylene disilanol monomer compounds. The solvent for use in the process is a mixture of absolute ethanol and anhydrous tetrahydrofuran. For the perspective of industrial applications, since the production of absolute ethanol is pricier than that of methanol, its selling prices are high, and thus its usage cannot reduce process costs significantly.
Furthermore, the prior art discloses that the treatment process of the para-phenylene disilanol monomer compounds not only requires effectuating neutralization with a potassium dihydrogen phosphate buffered solution, but also entails performing an intricate aqueous solution treatment process and product purification process, and its separation and purification techniques are not feasible for mass production, which produce excessive process wastes, incur high process costs, lack industrial applicability and mass production feasibility.
Therefore, it is an objective of the present invention to overcome the aforesaid drawbacks which confront the reaction process as well as separation and purification processes and promote the industrial applications for non-inflammable silicone polymer materials by developing a polymer with alternating phenylene silicon structure and siloxane structure and a precursor thereof.
Accordingly, it is imperative to provide a polymer with alternating phenylene silicon and siloxane structure and a method of producing a precursor of the same and develop an autonomous synthesis process of phenylene disilanol monomers for direct use in a subsequent polymerization reaction, without performing any additional purification and separation processes. Furthermore, it is imperative to provide a simple method of producing the polymer as well as separation and purification processes thereof to thereby effectuate ease of process and attain economic benefits, thus producing a polymer which comprises phenylene silicon and siloxane and meets industrial needs.